1. Field of the Invention
The present invention relates to an antenna device and a radio communication device.
2. Related Art
Because of the advantages of low distortion and low loss, the use of a MEMS (Micro Electro Mechanical System) capacitor as a variable capacitor for a tunable antenna has been researched. There has also been researched the use of a MEMS bank which varies its capacitance value by switching the ON/OFF states of a plurality of MEMS capacitors connected in parallel to create different combinations of the ON/OFF states.
However, a MEMS capacitor is a mechanical part and may suffer from the problem of stiction specific to MEMS elements, which is a phenomenon where electrodes may cling to each other during repetitions of ON/OFF operation and lock up in ON state. To cope with this, it is conceivable to provide in advance a spare MEMS capacitor to serve as a substitute for a locked-up element. However, the additional capacitance of the locked-up MEMS capacitor increases the lowest capacitance value. As a result, the frequency is shifted to the low-frequency side, thereby preventing achievement of a desired high frequency.    Non-patent Document 1: Gabriel M. Rebeiz, “RF MEMS: Theory, Design and Technology”